Japan battled to save a nuclear power station from going into meltdown yesterday after a third explosion in three days erupted at the damaged plant and fuel rods at a reactor were left fully exposed, with staff now struggling to cool the rods in three reactors.

While officials sought to reassure the public that the explosion posed no immediate health threat, the latest flurry of incidents has added to an already tense mood and raised concerns about the ability of the authorities to take a proactive grip of the situation. In an indication of the concern about the possible threat from radiation, US authorities relocated vessels from the 7th Fleet operating in Japanese waters off the coast from Fukushima after detecting low-level radiation on 17 crew members who have been taking part in relief operations.

In Sendai, the nearest large city to the epicentre of the earthquake, news of the nuclear setbacks came with fresh warnings about further possible tremors and another tsunami wave.